Security audit

The buffer space (or memory) for queues is finite in capacity and acts very much like a funnel for water that is being poured into a small opening. If water continually is entering the funnel much faster than it exits, eventually the funnel begins to overflow from the top. When queuing buffers begin overflowing, packets might be dropped either as they arrive (tail drop) or selectively, before all buffers are filled. Selective dropping of packets when the queues are filling is referred to as congestion avoidance. Congestion-avoidance mechanisms work best with TCP-based applications because selective dropping of packets causes the TCP windowing mechanisms to throttle back and adjust the rate of flows to manageable rates.

Congestion-avoidance mechanisms are complementary to queuing algorithms and are discussed in more detail in Congestion-Avoidance Tools. The relationship between congestion-management tools (or scheduling algorithms) and security audit is as follows: With congestion management, the scheduling algorithms manage the front of a queue; with congestion avoidance, the mechanisms manage the tail of a queue.